how to prevent injury in the classroom - cornell...

Ergonomics and Children: How to prevent Injury in the Classroom

Professor Alan HedgeCornell University

Dept. Design & Environmental AnalysisIthaca, NY 14853-4401

With thanks to Kathryn Laeser, Shawn Oates, Prof. Gary Evans & Prof. Lorraine Maxwell.

Session presented at the National Ergonomics Conference, Anaheim, 6-9 Dec., 1999.

Presentation Content

Computer use in schools

Children and computer use -issues + research evidence

Implications and future action

Conceptual Framework

LatencyMass computerization of the office in the 1980s is associated with the increase in WMSDs in the 1990'sMass computerization of the schools in the 1990's …?

Lifelong habitsLearning good posture and work habits requires the same effort as learning poor posture and work habits.

Children as small adults (biomechanically)

Computers in Schools

Computer use in schools inevitably is increasingComputer ergonomics is a lifelong skill (Larson, 1999).

Tomorrow's workers are in today's schools

Computers in Schools(Coley, Policy Information Center, ETS, 1999)

98% of all schools own computers4.4 million computers in classroomsCurrent average student-to-computer ratio:

10:1 (range 6:1 – Florida, Wyoming, Alaska, North Dakota to 16:1 –Louisiana), down from 125:1 in 1984.11:1 – Elementary schools9.7:1 – Junior High8.4:1 – Senior High

Computers in Schools(Coley, Policy Information Center, ETS, 1999)

85% of schools have multi-media computers (MMC) [Keyboard + mouse]Current average student-to-MMC ratio is 24:1 (range 9:1 – Florida to 63:1 – Louisiana). US Dept. Education currently recommends a ratio of 5:1

School Computers use by Children(Coley, Policy Information Center, ETS, 1999)

Daily computer use in schools:4th grade – 9%8th grade – 10%12th grade – 19%

Computer integration into the curriculum (work, games)Internet access

1998- 51% schools1999 - 89% schools

One computer per desk policies

Computers use by Children(AOL & Roper Starch, 1999)

Computers in schools and homes1-3 hours per day computer use and growing63% of 9-17 year olds prefer web surfing to watching TV

Computers use by Children(AOL & Roper Starch, 1999)

Average on-line days per week:9-11 years old - 3 days/week15-17 years old - 5 days/week

Internet:Rookies average 6.6 hours/weekExperienced users (> 3 years) average 10.5 hours/week

Computer Use by Children(AOL Canada, 1999)

~ 5 million children <12 years old use the InternetBy 2002, ~20 million children <12 years old will be using the Internet

Lifelong Computer Use(Berenter, Greenhouse & Webster, + Fortino Group, 1999)

Survey of 162 children 9-12 years, 6,000 children 10-17 years oldChildren who use the Internet > 3 times/week spend only 66% time reading compared with non-users.Internet savvy kids score more 'As' in school, but do worse in spelling, punctuation and grammar.

Lifelong Computer Use(Berenter, Greenhouse & Webster, + Fortino Group, 1999)

At present rates, during their lives children will spend >2 years on e-mailAt present rates, during their

lives children will spend at least 23 years on the Internet

Technology Integration In SchoolsSchool Technology integration plans typically do not address ergonomic workstation design issues

Typical Technology Plan (e.g. ICSD, 1995)Teacher trainingUpdating building infrastructure (power, network)Hardware and software acquisition

United States Congressional Study (1995)“America’s Schools not designed or equipped for the 21st Century”

School Technology Plans

Plans focus on the technologyPlans do not incorporate consideration of ergonomic issues.

Ergonomic Design Issues

Environmental conditions for computers:

LightingVentilation (heat, IAQ)Cable management/electrical fields

Furniture for computer workWorksurfaceMonitor heightKeyboard trayMouse platformDocument holderChair

Layout for computer workWorkstation layoutClassroom layout

Ergonomic Design QuestionsHow should computer workstation design be addressed in school technology integration plans?

What is the impact of computer workstation design on a student’s physical well-being

What is the impact of workstation design on the effectiveness of computer use

Research Studies

“At Risk” Postures

In adults, sustained work in a deviated posture can increase injury risks to the upper body.What happens in children?

"At Risk" Typing Posture in Adults (‘Yuppie hunch’)

Extended wrist

Stoopedshoulders

Extended neck

Monitor too low and too close

Acute elbow angle

Kyphoticback

"At Risk" Mouse Use Posture in Adults

Twistedtorso

Abducted shoulder Extended wrist

Hand posture: Lateral deviations

Neutral PostureRelaxed wrist with

the hand in a neutral posture.

Radial DeviationDeviated posture

causes wrist strain.

Ulnar DeviationDeviated posture

causes wrist strain.

0.020.040.060.080.0

100.0120.0140.0160.0180.0200.0

(40.0)(30.0)(20.0)(10.0) 0.0 10.0 20.0 30.0 40.0

Ulnar deviation Radial deviation

ICP(mmHg)

Lateral Deviation and ICP(Rempel, 1992)

Angle

Neutral zone

Hand posture: Vertical deviations

Neutral PostureRelaxed wrist with

the hand in a neutral posture.

Wrist ExtensionDeviated posture

causes wrist strain.

Wrist FlexionDeviated posture

causes wrist strain.

Vertical Deviation and ICP(Honan et al., 1995)

Neutral zone0

20

40

60

80

100

120

140

-60 -50 -40 -30 -20 -10 0 10 20 30 40 50

intra

carp

alpr

essu

re (m

m H

g)

extension flexion

Neutral Zone of Hand Movement(Hedge, 1998)

Hand movements within a neutral range should be encouragedIs this how children work on computers?

Neutral Work PostureUpper body posture

Back supported by chairFeet firmly on surfaceHead balanced on neckPopliteal angle >90°Upper arms close to bodyElbow angle >90°Wrist neutral (<15°)

How are children working at computers?

Children’s Posture at Computers(Oates, Evans and Hedge, Computers in Schools, 14, 55-63, 1998)

95 elementary school children (46 boys, 49 girls)Grades 3 through 5 studiedAges 8.5 – 11.5 yearsApprox. equal numbers at the 5th, 50th and 95th %iles for statureUrban, suburban and rural schools studied

Research Procedure(Oates, Evans and Hedge, Computers in Schools, 14, 55-63, 1998)

Children evaluated in their typical computer work areaChildren evaluated while working on a novel text-writing taskWorkspace dimensions and layout recordedPosture evaluated using the Rapid Upper Limb Assessment (RULA) methodRULA measures taken after 5 minutes of work

Workstation Dimensions(Oates, Evans and Hedge, Computers in Schools, 14, 55-63, 1998)

90 ° - 108°90 ° - 120°Back rest angle

11.8 – 17.7”13 – 15”Seat pan width

23.6 – 31.5”26 – 30”Backrest height

37.4 – 51.2”31.5 – 38”Monitor height

25.6 –39.4”21.5 – 24”Keyboard height

ObservedRecommendedDimension

Interpretation of RULA Scores

(1-2) Posture is acceptable if it is not repeated for long periods of time.(3-4) Further investigation is needed and changes are required.(5-6) Further investigation and changes are required very soon.(7) Further investigation and changes are required immediately.

Overall RULA Results(Oates, Evans and Hedge, Computers in Schools, 14, 55-63, 1998)

0

5

10

15

20

25

30

35

1 2 3 4 5 6 7

RULA s c or e

# c h ild r e n

RULA: ‘At Risk’ Body Segments(Oates, Evans and Hedge, Computers in Schools, 14, 55-63, 1998)

0102030405060708090

100

Neck Lowerarm

Wrist Leg

%Grade 3Grade 4Grade 5

Research Conclusions(Oates, Evans and Hedge, Computers in Schools, 14, 55-63, 1998)

Children working in ‘at risk’ postures:

Keyboards too highIncorrect keyboard angleMonitors too highLegs dangling

Short duration of computer workMarked lack of attention and commitment to consideration of ergonomic issues in schools

Ergonomic Solutions for Better Posture?

DeskTray

(Stack, 1988)

Tiltdown system

Improving Workstation Ergonomics(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

Tested effects of computer workstation design on:

PostureTask performanceEngaged behaviorPreferences

Studied keyboard and mouse useCompared conventional andtiltdown keyboard arrangements

Research Design(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

58 middle school children tested:30 6th grade students28 8th grade students

Research Design(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

Keyboarding and mousing tasks performed under two conditions:

desktop arrangementtiltdown keyboard system

Research Design(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

Keyboarding and mousing tasks performed under two conditions:

desktop arrangementtiltdown keyboard system

Experimental Measures (Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

PostureRULA method

Performancecomputer program for each task

Engaged Behaviorvideo tapes

Preferencesinterview

6th Grade: keyboard and mouse use(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

6th grader using the keyboard on the table top set at the height of the school computer surfaces.

6th Grade: keyboard and mouse use(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

6th grader using the keyboard on a tiltdown tray system.

6th Grade: keyboard and mouse use(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

6th grader using the mouse on the table top set at the height of the school computer surfaces.

6th Grade: keyboard and mouse use(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

6th grader using the mouse on a lowered platform.

8th Grade: keyboard and mouse use(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

8th grader using the keyboard on the table top set at the height of the school computer surfaces.

8th Grade: keyboard and mouse use(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

8th grader using the keyboard on a tiltdown tray system.

8th Grade: keyboard and mouse use(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

8th grader using the mouse on the table top set at the height of the school computer surfaces.

8th Grade: keyboard and mouse use(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

8th grader using the mouse on a lowered platform.

8th Grade: keyboard and mouse use(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

Tall 8th grader using the keyboard on the table top set at the height of the school computer surfaces.

8th Grade: keyboard and mouse use(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

Tall 8th grader using the keyboard on a tiltdown tray system.

8th Grade: keyboard and mouse use(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

Tall 8th grader using the mouse on a lowered platform.

Posture(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

Results confirmed that seated posture improved when the workstation had the adjustable tiltdown system:

keyboarding (p<.001)mousing (p<.001)

Posture Improvements(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

Keyboard Use

1

1.5

2

2.5

3

3.5

4

Upper arm Forearm Wrist Trunk

Mean RULA rating

Conventional Ergonomic

Posture Improvements(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

Mouse Use

1

1.5

2

2.5

3

3.5

4

4.5

Upper arm Forearm Wrist Trunk

Mean RULA rating

Conventional Ergonomic

Performance(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

Typing performancesmall but significant decrease with Ergonomic arrangement (<1%: p<.001)Likely can be overcome with practice

Mousing performancesmall but significant improvement with Ergonomic arrangement (3%: p=.018)may be due to change in posture or possibly improved mouse pad surface

Engaged Behavior(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

Increased distractions and decreased on-task time occur with a mismatch between seating arrangement and the nature of the learning activity (Hastings & Schweiso, 1993).

Differences in on-task time were not statistically significantly different in our study, but a longer duration testing period may be required to properly assess this.

Student Preferences(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

38% of students chose the tiltdownsystem as the workstation they would rather work at.33% stated that the tiltdown system was more comfortable than the desktop arrangement40% chose the tiltdown system as the workstation that was easier to work at.

Limitations of the Study(Laeser, Maxwell & Hedge, J. Res. Comp. Ed., 31, 173-188, 1998)

Implications limited to immediate effects of the workstationStudents all from the same schoolUnequal number of males and femalesSelf-selection – volunteer sampleNormal ability childrenDesktop computer

Laptop Computers in Schools

http://www.ammsa.com/sage/APRIL99.html

Laptop Computers in SchoolsIn 1995, the then House Speaker, Newt Gingrich, proposed putting a laptop computer in the hands of every schoolchild in America. In isolated pockets around the country, it's happening at a frenzied pace, in both private and public schools." (http://www.csmonitor.com/durable/1998/06/09/p51s1.htm)

Laptop Computers in Schools

In 1997 the chairman of the Texas Board of Education, proposed buying laptops for all 3.8 million public-school students in the state.

(http://www.csmonitor.com/durable/1998/06/09/p51s1.htm)

Laptop Computers in SchoolsAccording to Microsoft Corp., in the last two years computer software and hardware companies have encouraged 250 middle and high schools to lease or loan the computers to about 40,000 students nationwide. They note that "the idea is so popular with parents that many districts have plans to double or even triple the number of participants by next fall."(http://www.csmonitor.com/durable/1998/06/09/p51s1.htm)

Laptop Computers(Harris & Straker, Int. J. Indust. Erg. 2000 in press)

Surveyed 314 10-17 years old childrenInterviewed and observed 20 childrenMean daily laptop use = 3.2 hrsMean weekly laptop use = 16.9 hours60% reported postural;l discomfortDiscomfort correlated with time of use per session, not days of use

Laptop Recommendations(Harris & Straker, Int. J. Indust. Erg. 2000 in press)

Laptop use associated with poor posture and musculoskeletal discomfortLaptop design - need to separate keyboard and screenEncourage neutral, supported posturesTake frequent breaks, stretch, moveUse the lightest laptop (carrying also associated with discomfort) + best screen

Conclusions

Workstation design influences a child’s posture and their computer task performance.Children often adopt ‘at risk’ postures when using computers.Postural risk can be reduced with task-appropriate and ergonomically designed workstations, and with ergonomic training.Exposure can be managed and minimized by monitoring use time + stretch breaks.

Future Issues and Recommendations

Research NeedsSurveys of different grades, differently-abled childrenStudents workstation redesign/retrofitting to facilitate healthier posturesDurability of adjustable workstations in educational environmentsTeacher and student training in healthy computer work postureOther school ergonomic issues (backpacks, laptops, visual effects etc.)

Recommended Actions

Schools should consider the ergonomic implications of classroom computer useSchools should train students in good ergonomic practices and healthful posturesSchools should budget for appropriate workstations to support computer useParents should consider ergonomic issues with home computer useComputer use time should be managed to control exposures at school and home

Protecting Our FutureAs Ergonomists, we have a responsibility to use our professional knowledge of ergonomic solutions to protect future generations against unnecessary exposures to musculoskeletal injury risks.

(Source:Time Digital, 1998)